Lubricant and method of making same



Patented Oct. 20, 1936 A UNITED STATES PATENT OFFICE LUBRICANT AND IMETHOD 0F MAKmG. SAME of New York No Drawing. Application November 16, 1935, Serial No. 50.238

The design of automotive engines h at present tending toward the use of higher compression and higher rotative speeds and is encountering higher crankcase temperatures and higher hearing pressures. This is resulting in a departure from the use of bearing metals of the usual types such as babbitt. Thebearing metals coming into the general use are of different natures, but as a general thing although they are harder, they are more susceptible to destructive agencies of a corrosive nature. Typical of these newer bearing metals are those composed of cadmiumsilver alloys, cadmium-nickel alloys, and copper lead alloys. One widely used type of bearing of the newer kind is composed of a cadmium-silver alloy supported upon a steel back.

Concurrent with changes in engine design have been marked advances in methods of refining lubricant oils for automotive use, due to the sharp demand for oils having a low rate of change of viscosity with temperature; that is oils of a high viscosity index (V. 1.). This demand for such oils has been met by refining lubricants intended for motor oils with certain solvent extraction processes. In these processes advantage is taken of the fact that numerous reagents, such as for example dichlorodiethylether, cresylic acid, phenol, chloraniline, chlorophenol, phenetidine, benzyl alcohol, nitrobenzene, benzonitrile, furi'ural, aniline, benzyl acetate, liquid sulphur dioxide, a mixture of liquid sulphur dioxide or aniline with benzol, and the like, have selective solvent power for hydrocarbons of various types. These solvent refining processes are operated in a manner which concentrates in the desired lubricating fractionation, those compounds of a paraflinic nature which have a low susceptibility to change of viscosity with change in temperature or in other words, a high viscosity index. In doing this, they reject from the desired lubricant those compounds of naphthenic nature which have a low viscosity index. These processes have enabled the supply of an oil of highly'desirable general characteristics definitely far superior to any oil previously produced from mixed base or asphaltic crudes and superior to a like, although lesser, degree over oils previously'produced from paraflin base crudes. It has been found that motor oils produced by the solvent refining process referred to above are definitely corrosive to the newer bearing metals mder normal conditions of automotive use, and in extreme cases their corrosive properties have been so great as to result in bearing failure after only a few thousand miles of normal driving. It is filrther known that the same reaction, via, corrosion of alloy bearing metals such as cadmium-silver, also occurs in good paraflinic base oils which have not been subjected to solvent refining. The degree of corrosiveness apparently rises with the viscosity index, since with oils of higher viscosity index, the tendency to corrosion of the kind referred to above is more pronounced. Speaking in general terms, corrosion of this nature is encountered to a recognizable degree in oils having a V. I. of or higher, becoming important in amount in oils having a V. I. of to or higher, and very serious in nature in oils of V. L or higher.

It is an important object of this invention to provide means for satisfactorily inhibiting or preventing this corrosion from taking place to a serious degree. It is an object of this invention to alter or modify a highly refined motor oil, normally corrosive, by use of an additive ingredient capable of substantially inhibiting this corrosion. It is an object to provide a substantially non-corrosive motor oil of high V. I. An object of this invention is to provide an additive reagent or ingredient capable of inhibiting the corrosive properties of these oils. The production of solvent refined oils of low corrosive properties under conditions of automotive use is a major object of this invention, as well as the method of production of such oils which couple high viscosity index with low tendency to corrosion.

This invention is based on the discovery that the addition to the oil of small amounts of a tricresylphosphite (CH3CsH40)3P, accomplishes the above object. It is found that when carrosion of the type referred to above occurs, especially if it occursin the presence of a motor oil which has been produced by a process of solvent refining, in which type of oil the corrosive properties appear to be more marked, that the oil can be rendered substantially non-corrosive under conditions much more strenuous than normal automotive use by the addition of controlled amounts of this compound, a tricresylphosphite. The tricresylphosphites are isomeric organic compoundshaving the following graphic formula:

This compound may be prepared by the reaction of ortho-cresol or meta-cresolor para-cresol or mixtures thereof and phosphorous trichloride, in the proportions of three molecular amounts of the cresol or mixed cresols to one molecular amount of phosphorous trichloride. The reaction mixture is heated until the evolution of hydrogen chloride ceases. The resulting product, a tricresylphosphite, may be purified if desired by a process of fractional distillation. For the present objects, it may be used either as produced or in the fractionated form. A satisfactory reaction product may be made by heating the reaction mixture after the cessation of the evolution of 1101 gas to a-temperature of 200 C. under a pressure of 2 mercury. The product so made is designated hereinafter as topped. The following data demonstrate the efiectiveness of this ,novel corrosion inhibitor. In these tests a motor oil of S. A. E. 20 rating, having a Saybolt viscosity of 56.6" at 210 F., a flash point Of 425 F. and a V. I.- of 117 was-used, this oilbeing an .oil which had been subjected to a high degree of solveht refining. Actual motor operation tests are set forth in Table 1 below. In these tests, a motor oil blank and motor oil blends containing different proportions of the novel corrosion inhibiting ingredient of this invention were subjected to test in a modified Delco knock test engine, equipped with. bearings of cadmium-silver alloy on a steel back. The alloy is about 2.5% silver, a few hundredths of a per cent of copper and the'balance' of cadmium. The motor was equipped with crankcase oil heaters to'maintain 'oil'temperatures (330 F.) at least equal to those encountered under extreme conditions of automotive use. on each test, the test engine was operated for 40 hours, at a rotative speed the equivalent of an automobile road speed of 60 miles per hour. In rough terms each test is the equivalent of exposure of the oil to use in an automobile for 2400 miles of continuous driving at 60 miles per hour, a condition far more rigorous than any encountered in normal use. The bearings in the engine were new for each test and were carefully weighed before and after to determine loss of weight. The neutralization number (N. N.) of the used oil was measured and is recorded as being indicative of the corrosive nature of the oil. The in-v hibitor used was the mixed isomeric tricresylr An indicative test of considerable merit may be made in the laboratory by suspending a portion of a cadmium-silver alloy bearing in a bath of the oil under test in a glass container, maintaining the oil at about 350 F., and passing air through the oil in contact with the bearing metal. Convenlent conditions are: gm. oil, 2,000 ml. air per hour, 22 hours. The following table shows retralization number of the used oil. The oil used was the same as in Tagle I.

Table II Cadmiumas; iwe g 0 use change in oil milligrams Oil blank (8. E. A. 20) 38. 3 2. 60 Oil with 0.10% triorthocresyl-phospbite-a- +0. 2 0. 42 Oil with 0.26% triottliocresyl-pbosphite- 0. 5 0. 64 Oil blank (8. A. E. -L 68. 7 2. 30 Oil with 0.10% mixed tricresylphosphites... i 1. 8 0.40

' From these tests, it'is evident that the use of this novel corrosion inhibitor, viz., tricresylphosphite, in amounts as small as 0.10% prevented corrosion to a substantially complete degree under conf-ditions much more rigorous than any likely to be met in practice.

- {From the combined evidence of the above exemplary data, it is evident that the novel corrosi'on inhibiting ingredients herein disclosed, namelytricresylphosphites are eflfective agents for the prevntionpi corrosion of automotive parts, particularly the newer type alloy bearings, when introduced in proper amounts into an oil otherwise highly corrosive.

Visual examination of the bearings from engine tests such as those reported in Table I show the effectiveness of tricresylphosphites in a very .marked manner. The bearing subjected to the .oil blank shows plainly the eifect' of corrosion,

'very little of the original surface remaining. The bearings subjected to the inhibited oils show little or no visual evidence of corrosion. Similar visual evidence of the efiectiveness of this inhibitor may be noted by inspection of the pieces of metal used in the tests in glass. 7 It is, preferred to use this ingredient, a tricresylphosphite, in amounts ranging between 0.25% and 1.0% although for less severe services and in oils not highly corrosive, -as low as 0.10% may be fully efiective for the purpose intended.

These ingredients, tricresylphosphites, are

waterclear oils freely miscible with hydrocarbons,

and may be added in any proportion without darkening or deepening the color of the oil. When so added, they have no tendency to separate from the oil under conditions of storage or use;

' We claim: I

1. A m'etho'd'of lubricating bearing surfaces in internal combustion engines when subjected to conditions of operation which comprises maintaining between bearing surfaces, one of which is an alloy formed chiefly of a metal selectedirom the class consisting of cadmium and copper, a film of lubricating oil which initially produces an cife'ctive lubricating. action but which would normally tend to corrode the aforesaid alloy, and maintaining the efiectiveness of the lubricating oil byincorporating therein tricresylphosphite in a small but sufficient proportion substantially to retard the corrosion;

2. A method of lubricating bearing surfaces in internal combustion engines when subjected to conditions of operation which comprises maintaining between bearing surfaces, one of which is an alloy formed chiefly of a metal selected from the class consisting of cadmium and copper, a film of lubricating oil which initially produces an eifective lubricating action but which would normally tend to corrode the aforesaid alloy, and maintaining the effectiveness of the lubricating oil by incorporating therein from 0.1% to 1.0% of tricresylphosphite suflicient substantially to retard the corrosion.

- 3. A method of lubricating bearing surfaces which comprises maintaining between bearing surfaces, one of which is an alloy selected from the class consisting of cadmium-silver, cadmiumnickel, and copper-lead alloys, a film of lubricating oil which initially produces an effective lubrieating action but which would normally tend to corrode the aforesaidalloy, and maintaining the T effectiveness of the lubricating oil by incorporating therein tricresylphosphite in a small but sufflcient proportion substantially to retard the corrosion.

4. A method of lubricating bearing surfaces which comprises maintaining between the bearing surfaces, one of which contains a characterizin proportion of cadmium, silver, nickel, copper or lead, a film of lubricating oil which initially produces an efiective lubricating action but which would normally tend to corrode the aforesaid surface, and maintaining the efiectiveness of the lubricating oil by incorporating therein tricresylphosphite in a small but suflicient proportion to substantially retard the corrosion.

ROBERT C. MORAN. WILLIAM L. EVERS. EVERETT W. FULLER. 

